#include <ftw.h> int nftw(const char *dirpath, int (*fn) (const char *fpath, const struct stat *sb, int typeflag, struct FTW *ftwbuf), int nopenfd, int flags); #include <ftw.h> int ftw(const char *dirpath, int (*fn) (const char *fpath, const struct stat *sb, int typeflag), int nopenfd);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
To avoid using up all of the calling process's file descriptors, nopenfd specifies the maximum number of directories that nftw() will hold open simultaneously. When the search depth exceeds this, nftw() will become slower because directories have to be closed and reopened. nftw() uses at most one file descriptor for each level in the directory tree.
For each entry found in the tree, nftw() calls fn() with four arguments: fpath, sb, typeflag, and ftwbuf. fpath is the pathname of the entry, and is expressed either as a pathname relative to the calling process's current working directory at the time of the call to nftw(), if dirpath was expressed as a relative pathname, or as an absolute pathname, if dirpath was expressed as an absolute pathname. sb is a pointer to the stat structure returned by a call to stat(2) for fpath. typeflag is an integer that has one of the following values:
The fourth argument that nftw() supplies when calling fn() is a structure of type FTW:
struct FTW {
int base;
int level;
};
base
is the offset of the filename (i.e., basename component)
in the pathname given in
fpath.
level
is the depth of
fpath
in the directory tree, relative to the root of the tree
(dirpath,
which has depth 0).
To stop the tree walk, fn() returns a nonzero value; this value will become the return value of nftw(). As long as fn() returns 0, nftw() will continue either until it has traversed the entire tree, in which case it will return zero, or until it encounters an error (such as a malloc(3) failure), in which case it will return -1.
Because nftw() uses dynamic data structures, the only safe way to exit out of a tree walk is to return a nonzero value from fn(). To allow a signal to terminate the walk without causing a memory leak, have the handler set a global flag that is checked by fn(). Don't use longjmp(3) unless the program is going to terminate.
The flags argument of nftw() is formed by ORing zero or more of the following flags:
Other return values could be associated with new actions in the future; fn() should not return values other than those listed above.
The feature test macro _GNU_SOURCE must be defined (before including any header files) in order to obtain the definition of FTW_ACTIONRETVAL from <ftw.h>.
If FTW_PHYS is not set, but FTW_DEPTH is set, then the function fn() is never called for a directory that would be a descendant of itself.
If fn() returns nonzero, then the tree walk is terminated and the value returned by fn() is returned as the result of ftw() or nftw().
If nftw() is called with the FTW_ACTIONRETVAL flag, then the only nonzero value that should be used by fn() to terminate the tree walk is FTW_STOP, and that value is returned as the result of nftw().
| Interface | Attribute | Value |
| nftw() | Thread safety | MT-Safe cwd |
| ftw() | Thread safety | MT-Safe |
The function nftw() and the use of FTW_SL with ftw() were introduced in SUSv1.
In some implementations (e.g., glibc), ftw() will never use FTW_SL, on other systems FTW_SL occurs only for symbolic links that do not point to an existing file, and again on other systems ftw() will use FTW_SL for each symbolic link. If fpath is a symbolic link and stat(2) failed, POSIX.1-2008 states that it is undefined whether FTW_NS or FTW_SL is passed in typeflag. For predictable results, use nftw().
#define _XOPEN_SOURCE 500 #include <ftw.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <stdint.h> static int display_info(const char *fpath, const struct stat *sb, int tflag, struct FTW *ftwbuf) { printf("%-3s %2d %7jd %-40s %d %s\n", (tflag == FTW_D) ? "d" : (tflag == FTW_DNR) ? "dnr" : (tflag == FTW_DP) ? "dp" : (tflag == FTW_F) ? "f" : (tflag == FTW_NS) ? "ns" : (tflag == FTW_SL) ? "sl" : (tflag == FTW_SLN) ? "sln" : "???", ftwbuf->level, (intmax_t) sb->st_size, fpath, ftwbuf->base, fpath + ftwbuf->base); return 0; /* To tell nftw() to continue */ } int main(int argc, char *argv[]) { int flags = 0; if (argc > 2 && strchr(argv[2], 'd') != NULL) flags |= FTW_DEPTH; if (argc > 2 && strchr(argv[2], 'p') != NULL) flags |= FTW_PHYS; if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags) == -1) { perror("nftw"); exit(EXIT_FAILURE); } exit(EXIT_SUCCESS); }